The present invention relates to a device and a method for sterilising plastic containers and in particular plastic parisons. It is known from the prior art that in the context of the production of beverage containers the containers to be filled are also sterilised to some extent. For this purpose in the prior art sterilisation methods are usually used which employ chemical agents, such as for instance hydrogen peroxide or peracetic acid. Recently, however, attempts have been made to dispense with the use of such chemicals. Accordingly devices and methods are also known from the prior art in which the sterilisation takes place by the use of radiation sources, such as for example ultraviolet light or also electron radiation sources. The present invention is therefore described in particular with reference to sterilising devices which apply charge carriers to the containers in order to sterilise the containers.
The current devices which are available on the market and are used for sterilisation usually have an electron generating device and also a beam finger which serves for disinfection of the internal surfaces of the containers. In addition such system also has electron generating devices which also treat the internal surfaces from the exterior through the container. In the treatment from the exterior the electrons must generally be accelerated considerably more, since the wall of the container to be treated must be penetrated and in spite of the weakening the electrons must always still contain sufficient energy in order to act to sterilise the inner surface. The X-ray radiation produced in this case must be screened off from the environment by suitable screens. In addition the entire container material is loaded with a radiation dose.
Arrangements which operate with a beam finger generally use substantially lower acceleration voltages and thus fewer shields and lower radiation doses in the container material. However, in order also to sterilise the containers externally a further process step is necessary. The external treatment can be carried out before, during or also after the internal treatment.
The object of the present invention therefore is to provide a device and a method which enable an improved external sterilisation of the containers and preferably also an improved overall sterilisation thereof.